Experimental study of emission characteristics for fully premixed combustion of dimethyl ether and hydrogen based on flame ions

The detection of flame ion current is a promising approach in fully premixed combustion. However, how to control the excess air coefficient ( alpha) by ion current still needs an effective method. For this reason, the application of natural gas (12T), hydrogen -doped 12T (12T -H) and dimethyl ether (DME) in fully premixed combustion is experimentally studied in this paper. The emission characteristics of NO x , CO and CO 2 from fully premixed condensing gas boilers (FPCGB) were analyzed. The detection voltage generated by the flame ion current is used to monitor the NO x emissions of different gas types. A novel combustion control method based on flame ion current is proposed. The results show that hydrogen addition can reduce NO x , CO and CO 2 emissions of 12T. The highest NO x emission is observed at a hydrogen volume ratio (HVR) of 15 % in the experiment. The detection voltage gradually decreases with increasing HVR. The CO 2 of DME is always lower than 12T. When alpha exceeds 1.21, 1.31 and 1.12, respectively, DME exhibits higher values in NO x , CO and detection voltage compared to that of 12T. In addition, two combustion characteristic values are identified and proposed for combustion feedback control. The peak voltage (U p ) can be used as a parameter to identify the type of gas. The emission voltage (U e ) can be used to determine whether the NO x emission concentration exceeds the 40 ppm threshold.